One of my favorite things to do is READ and encourage children to read as well. As part of an academy course I taught on the Daily 5, I began to collect websites for reading. These are in no particular order.

TweenTribune- by the Smithsonian
Forgotten Books
Book Track Classroom- creating audio books
Unite For Literacy- thousands of free books online
Clifford the Big Red Dog Interactive books
1000 Books before Kindergarten
A Story before Bed- partially free
Zing- free classroom access to thousands of books
Project Gutenberg- free books
EPIC!- free for teachers- paid for families
ReadWorks- Free articles on all levels from K-12. Lesson plans and articles are downloadable. Provides Lexile and suggestions for how to use with different leveled students.